Is there any swimming holes that the kids can put their blow up innertubes in?

There are a few, especially this time of the year water level is low so there are actually many places where the water is clear and low

A lot of people were swimming in a section of the river when I was there, so I wouldn't think that would be a problem.

Yes, south falls has a swimming area

Yes there is a lil play area where water is low.. and toddlers can play its not deep.